I’m on the hunt for the origins of the phrase “practicably irrigable”. If anyone has any insights, please jump in on the comments. Here’s what I know:

The concept is central to water law in the western United States. The first reference I’m able to find in the U.S. legal canon is in the 1960 recommendations of Simon Rifkind, special master to the U.S. Supreme Court, in the case of Arizona v. California. Rifkind was trying to find a path to the quantification of Native American water rights:

This brings us to the question of quantity. This is sharply debated, and many conflicting views have been advanced. I have concluded that the United States effectuated the intention to provide for the future needs of the Indians by reserving sufficient water to irrigate all of the practicably irrigable lands in a Reservation and to supply related stock and domestic uses. The magnitude of the water rights created by the United States is measured by the amount of irrigable land set aside within a Reservation, not by the number of Indians inhabiting it. (emphasis added)

The court (sort of) adopted Rifkind’s thinking:

We also agree with the Master’s conclusion as to the quantity of water intended to be reserved. He found that the water was intended to satisfy the future as well as the present needs of the Indian Reservations and ruled that enough water was reserved to irrigate all the practicably irrigable acreage on the reservations. Arizona, on the other hand, contends that the quantity of water reserved should be measured by the Indians’ “reasonably foreseeable needs,” which, in fact, means by the number of Indians. How many Indians there will be and what their future needs will be can only be guessed. We have concluded, as did the Master, that the only feasible and fair way by which reserved water for the reservations can be measured is irrigable acreage. (emphasis added)

I can find no earlier references for the explicit phrase in the U.S. legal literature. But I did find this (JSTOR gated), an article by someone named William H. Wynne about Australian land development published in 1927:

In the southeast, where practically all the scanty rivers of the continent lie, there are, within the 10-inch line, vast tracts of semiarid land. But even of this only a small proportion can ever be brought within the range of irrigation; the greater part can be slowly reclaimed only through the practice and improvement of dry-farming methods. Nevertheless, the territory which is practicably irrigable and which, in consequence, may be made to support eventually a closely settled rural population engaged in market gardening, fruit-growing, mixed or dairy farming, comprises several million acres. But irrigation is costly, and, with the burden of public debt already heavy, it must of necessity proceed slowly. (emphasis added)

It’s such a weird phrase tied to such a narrow concept that I’ve got to believe there’s some dotted line connecting Wynne and Rifkind, but I can’t find it. Can you help?

Another thing I know: “practicably” is the single most difficult to pronounce word in the English language. Really. Add “irrigable”, which ain’t easy in its own right, and you create a world of flustered law professors.